Magnetization hysteresis and time decay measurements in FeSe$_{0.50}$Te$_{0.50}$ : Evidence for fluctuation in mean free path induced pinning

TL;DR

This study investigates vortex pinning mechanisms in FeSe$_{0.5}$Te$_{0.5}$, revealing that fluctuations in the mean free path induce weak pinning centers, affecting the vortex phase diagram and second magnetization peak behavior.

Contribution

It provides new evidence that spatial variations in mean free path cause vortex pinning in FeSe$_{0.5}$Te$_{0.5}$, linking microscopic disorder to macroscopic magnetic properties.

Findings

Pinning related to mean free path fluctuations causes the second magnetization peak.

Weak pinning centers are distributed randomly, affecting vortex dynamics.

Comparison with CeRu$_2$ peak effect highlights similarities in vortex behavior.

Abstract

We present results of magnetic measurements relating to vortex phase diagram in a single crystal of FeSe$_{0.5}$Te$_{0.5}$ which displays second magnetization peak anomaly for $H \parallel c$. The possible role of the crystalline anisotropy on vortex pinning is explored via magnetic torque magnetometry. We present evidence in favor of pinning related to spatial variations of the charge carrier mean free path leading to small bundle vortex pinning by randomly distributed (weak) pinning centers for both $H \parallel c$ and $H \perp c$. This is further corroborated using magnetization data for $H \parallel c$ in a single crystal of FeSe$_{0.35}$Te$_{0.65}$. Dynamical response across second magnetization peak (SMP) anomaly in FeSe$_{0.5}$Te$_{0.5}$ has been compared with that across the well researched phenomenon of peak effect (PE) in a single crystal of CeRu$_2$.